By Kelley Brummett, DMD 

A situation occurred in my office when I was working with a patient who needed a 30-year-old PFM crown replaced on #8. I was struggling with the shade because the adjacent teeth were an in between color. What I did was take a shade photo of the brightest one, which was B1, and then I took a shade photo with A1–because those were the two shades that matched the best. They weren’t what we were looking for. So, I made a provisional out of the A1 shade and a a provisional out of the B1 shade. I took the extra time to place both of them onto the tooth and let the patient look with me and help me decide. The patient chose the A1 shade. 

After I placed the A1 provisional, we sent  photos to my lab. These photos included the first shade photos of B1 and A1 alongside the tooth, photos of the B1 and A1 provisionals, and photos of the provisional I placed on the tooth from various aesthetic views. I then talked to the lab over the phone while we viewed the photos together so they could create the right in-between shade.  

At the end of the process, my patient expressed gratitude for taking the extra steps and meeting her expectations for a beautifully blended smile. 

Most of us are placing implant crowns, using screw retained crowns. If the crown needs to be recovered, or the screw needs to be changed or tightened, the restoration can be removed by accessing the screw through the screw channel.

One of the main advantages of screw-retained crowns is the ease of retrieval. I have discovered two ways to make retrieval easier for myself, which involve the colors of the Teflon tape and composite I use.

1. Now I have colored Teflon tape on hand, and when I place the screw, I put colored tape on top of the screw instead white tape. If I need to remove the composite, I more readily see my gray or yellow tape than I would white tape.
2. I also like to use a composite color that is not be an exact match with the implant crown. This way I can easily see the material to be removed to access the screw channel… if I need to remove the crown.

If you plan ahead to have colored Teflon tape on hand, you can do what I do. Teflon tape is available in multiple colors at Home Depot and other hardware stores.

How long does a dental crown last? The answer is, “It depends.” In this blog, I will review how I manage answering this question for my own peace of mind and to reduce disappointment for my patients.

All of us can think about crowns that are currently in our patients’ mouths that have been in four decades or more…crowns that are doing fine. Sometimes, we look at a bite wing of one of these restored teeth and see space enough “to drive a truck” between the margin and the natural tooth structure. Yet, the crowned tooth is fine with no caries.

We also can think about crowns in our patients’ mouths that needed to be or now need to be replaced within five years or under…perhaps, even within two years. Some of these crowns were carefully and beautifully done.

We have a habit of thinking: The better our skill is, the greater is the longevity of the crown. We need to get away from this generalization because there are numerous factors that impact longevity.

Yes, the dentist’s skill is a factor as are the amount of time and energy we put into making it exquisite, the quality of the laboratory, and the materials. But the other part of the equation is that we put dentistry into the mouths of human beings, and human beings come with risk factors. The most common reason we replace a crown or filling is recurring caries. We see some patients who have new carious lesions every time we see them in the dental chair. They are at high risk. At the other end of the spectrum, we have patients who have not had a carious lesion in multiple decades. The functional risk of the patient is the second primary risk factor. We have patients who can break any type of crown, and we have other patients who have no evidence of functional risk.

What do I say to my patients? I tell them dentistry does not last forever, and there are challenges in predicting the lifespan of their restorations. I do not say, “When your crown fails at some point in the future, it will need dental treatment again.” Instead, I say, “We’re going to treat this tooth with a crown. At some time in the future, it will need treatment again.” Then I say, “The most common reason why a crown needs to be replaced is dental decay around and under the crown, and what we know about you is that you tend to get cavities [or not get cavities]. The second most common reason we replace crowns is that they break. The materials cannot withstand the forces. And what we know about you is that you are tougher on your teeth [or not as tough on your teeth] compared to many other people. “

This type of conversation makes most dentists nervous. They fear the patient will not want to do the crown if the patient knows they will eventually need to retreat the tooth. That has not been my experience. The reality that cars do not run forever does not stop us from buying a new car. The knowledge that your roof will last 10 to 14 years does not stop us from replacing the roof. The reality that the tooth will need retreatment in the future does not stop us from having it treated now.

Setting realistic expectations results in less patient frustration, sadness, and disappointment. It also lessens conflict between the dentist and patients. I want my patients to understand the reality that dentistry does not last forever. It all has a lifespan, just like a car or washing machine. Any tooth we treat will need to be treated again. I also want them to know their risk factors for decay or breakage relative to other patients. Is it high? Is it low? Is it somewhere in between? We can then have a conversation about what they can do and what we can do together to minimize those risk factors.

Capturing an exquisite final impression is our goal every time. Getting this result can be one of the most challenging things we do in dentistry. In addition to being masterful in taking an impression and handling the materials, we also must manage the oral environment properly.

Improving the Gingival Tissue Prior to the Impression Appointment

For crown and bridge impressions this process has to begin with optimal tissue management, and tissue management always begins before tooth preparation. Old restorations with poor margins often compromise hygiene with resultant irritated and inflamed gingival tissues. If the tissue is inflamed at the time, we recommend the tooth be crowned, we apply chlorhexidine varnish (Cervitec Plus – Ivoclar Vivadent). When the patient returns for impressions, tissue health is vastly improved.

Managing the Gingival Tissue for Tooth Preparation

Tooth preparation itself can result in difficulty managing the tissue. My preference is always to leave margins supragingival if that is clinically appropriate. My second choice is equigingival, where the margins are right at the crest of the tissue. If the margins are to be placed subgingival, I want to avoid cutting the tissue and then having to manage bleeding. If my initial margin placement is equigingival, I place a primary cord to move the tissue out of the way. This allows me to now drop the margin subgingival with minimal trauma to the tissue.

Retraction of the Gingival Tissue for the Impression

Once tooth preparation is complete, retraction creates a space for the impression material to go past the margin apically so that we can create the proper emergence profile of the restoration. There are many ways to retract prior to an impression. I personally use a second or top cord with a larger diameter than the primary cord I placed to move the tissue for subgingival preparation. If the tissue is bleeding after the placement of the top cord, I place 3M’s “Retraction paste” as a hemostatic agent. This allows for optimal control of bleeding without worry of negatively impacting the set of my impression materials or staining the prep or gingival tissues.

Taking the Final Impression

The final impression is taken with Flexitime impression material (Kulzer). I have my assistant load the tray with heavy body material. I first wet the top cord, so I do not cause bleeding upon removal. The area is now thoroughly dried to allow for proper contact of the impression material to the tooth and tissue surfaces. I inject Flexitime CorrectFlow (Kulzer) and then seat the impression tray. I hold the tray for the full intra-oral set time and do not allow patients to close or bite on the tray, as movement can negatively impact the accuracy of the impression.

Is the impression perfect?

Once removed I inspect the impression using magnification to assess that I have adequate flash beyond the margins of the light body, no pulls, voids, drags or evidence that the impression moved. There is no way to correct an impression for errors. If errors occur, we repeat the process from the beginning to take a new impression.

Check out some of my short videos about impressions on Restorative Nation at https://restorativenation.com/?s=impression.